ROYAL OAK, Mich. (AP) — With just a few days of school left, teacher Shannon Smith knew she had to up her game to keep her room of third-grade students engaged in learning until the last day.

So Smith pulled out new educational materials she purchased from an online marketplace where teachers buy and sell teacher-created, teacher-tested educational materials.

Within minutes, her students at St. Mary Catholic School in Royal Oak transformed into detectives, exercising their critical thinking skills, trying to solve "The Case of the Missing Test."

"I can use it for any subject to enhance what I am doing," Smith said of materials on the site. "Even for geometry this year, I went though and found a triangle scavenger hunt. I'm looking to get the kids up and moving and interactive. It's fabulous."

Smith, like many teachers, paid for the extra educational materials out of her pocket to enrich the classroom experience. She estimates this school year, she has spent $95 on instructional materials and has done so in past years.

But under a new program that starts this summer, school administrators will use school funds to pay for extra educational materials for all 21 teachers at St Mary's.

The Detroit News reports that Teachers Pay Teachers, the online marketplace, created a program that allows administrators to set up school accounts for individual teachers who can build wish lists and make purchases.

There are 53 public and private schools in Michigan that are part of the schools program and about 100,000 active users, primarily teachers, company officials said.

"Three thousand schools are doing it today, and it's growing at 100 schools a week. Schools are finding real value in this," said Adam Freed, CEO of New York-based Teachers Pay Teachers, also known as TpT.

Freed said the program makes it easy for administrators and teachers to collaborate and make curriculum decisions together. Each teacher request comes with a detailed product description and a preview. There are also reviews from other teachers who have used the materials.

The TpT website has 3 million items to choose for teachers in grades pre-K through 12th and has been used by 5 million educators. Prices range from free to several hundred dollars for a full curriculum. The average cost of an item is $5.

Susan Hankins, principal at Memphis Elementary School, which has 400 students in grades K-5, signed up for the schools program last month.

"It's the ultimate classroom problem solver," Hankins said. "So many teachers are spending their own time creating these materials. TpT has saved them time, and it's great that they can share."

It was time for the school to step in and help teachers after watching them spend their own money on educational supplements for classrooms for years, Hankins said.

"We are really going to look are areas that need supplementing," she said. "I don't know yet what the budget will be for each teacher. I will do it on a case-by-case basis. Every grade level has different needs. I will fill in the gaps."

Linda Irwin, assistant principal at St. Mary's, said each teacher will get "a few hundred dollars" and can build wish lists this summer to buy materials for the coming school year. Irwin, who used the site as a teacher herself, said her teachers have full discretion to make their own choices.

"We could tell our teachers needed it and wanted it, they told us," Irwin said. "Part of that, too, is showing your teachers that you support them, and you are in their corner."

According to a study by the National Center of Education Statistics released in May, 94 percent of public school teachers say they spent $480 a year on items, such as notebooks, pens and other supplies in the 2014-15 school year without reimbursement.

Irwin said the school's decision to purchase a new science curriculum on Teachers Pay Teachers for grades 1-3 will help the school save money and provide teachers with more funds for their in-classroom needs, including school supplies.

The new curriculum was $55 per grade instead of $35 per student for new textbooks.

"We will not be using textbooks this school year in science," Irwin said. "The nice thing economically, it has saved us.

"Textbooks are expensive and they are consumable, so you are buying them every year. So we will be able to give the teachers a lot more supplies and hands on things they need in the classroom for science."